The present invention relates to circuitry for processing component video signals, and in particular, to circuitry for removing synchronization signals from component video signals.
As is well-known, computer monitors and, increasingly, many higher quality televisions, receive their display signals in the form of component video signals such as GBR (green, blue, red), YPbPr (luminance, blue difference, red difference). Typically, the first of the three channels (e.g., the green and luminance signals) contains a composite signal in which both the video (green or luminance) and synchronization (horizontal and vertical) components are included. As is also well-known, the Consumer Electronics Association (CEA) standards (e.g., CEA-770.1-C, CEA-770.2-C and CEA-770.3-C) for component video signals specify the component video signal also containing the synchronization component to be a one-volt peak-to-peak signal, with the one extreme signal peak (e.g., minimum or lower) being that of the tip of the synchronization signal component and the opposite extreme signal peak (e.g., maximum or upper) being that of the maximum level, i.e., white, of the video signal component. For example, in conformance with the CEA-770.1-C standard, these voltage levels are −286 mV (mV) and +714 mV, respectively, while for the CEA-770.2-C and CEA-770.3-C standards, these levels are −300 mV and +700 mV, respectively. (For all three of these standards, the voltage levels for the other two component signals, Pb and Pr, are −350 mV and +350 mV.)
Successful operation within the standards often requires removal of the synchronization signal excursions, or “tips”. One conventional technique removes the synchronization signal tips by forcing the signal containing the synchronization signal component, e.g. the luminance Y signal, to be fixed at or above the reference video black level. However, the tri-level synchronization signal used in high definition television (HDTV) analog component video signals (FIG. 1B) tends to be problematic since such technique cannot remove the synchronization tips completely, thereby often resulting in undesired residual signal components related to the original synchronization signal tips.